1. Field of the Invention
The present invention relates to an ultrasonic microscope.
2. Description of the Related Art
Conventionally disclosed in Japanese Patent Publication No. 59-44582 and Japanese Patent Disclosure No. 58-196453, for example, are ultrasonic microscopes in which a sample to be observed is two-dimensionally scanned with an ultrasonic beam, and the resulting transmitted or reflected waves are received to obtain an ultrasonic image of the sample.
Also, a cryogenic ultrasonic microscope capable of providing a high-resolution ultrasonic image is described in The Journal of Acoustic Society of America, vol. 67 (1980), pp. 1,629 to 1,637. In this microscope, a cryogenic fluid, such as liquid nitrogen, liquid argon, or liquid helium, which is lower in sound transmission speed and acoustic absorptivity than water, is used as an ultrasonic transmission medium interposed between an acoustic lens and a sample.
These conventional microscopes, however, are complicated in construction, and cannot enjoy a wide scanning range without lowering their operating efficiency.